Cardiovascular effects of enoximone in isoflurane anaesthetized ponies.

This research studied the effects of a heart medication called enoximone on ponies under general anesthesia. They found that it positively impacted the animal’s heart rate and the amount of blood pumped by the heart, without significantly changing the blood pressure.

Study Design and Methodology

• The study with prospective, randomised, and experimental design involved six healthy ponies, which were used to examine the impact of enoximone on isoflurane-anaesthetized ponies. Enoximone is a common drug used in human medicine to enhance the cardiac output—volume of blood pumped by the heart per minute.
• The ponies were first sedated using romifidine—an alpha-2 adrenoreceptor agonist for sedation. They were then anaesthetized using cocktails of midazolam and ketamine—a common combination for equine anesthesia
• After induction of anesthesia, the ponies were given isoflurane—an inhalational anesthetic—and ventilated to maintain a normal level of carbon dioxide in their blood
• The ponies were then given intravenous doses of either enoximone or saline 90 minutes after the anesthesia was induced. Each pony underwent anesthesia twice, with a break of three weeks between administrations.

Measurements and Outcomes

• Various parameters related to cardiovascular health were measured at different time points before and after the drug administration. These include heart rate, blood pressure, right atrial pressure, and cardiac output.
• Other parameters including stroke volume (the volume of blood pumped in one heart beat), systemic vascular resistance (resistance faced by blood when it is pumped through the circulatory system), and the volume and efficiency of oxygen delivered were also calculated.
• Enoximone was found to increase heart rate, cardiac output, stroke volume, and the amount and efficiency of oxygen delivered to the tissues. It also led to a significant decrease in right atrium pressure.
• There were no significant changes detected in arterial pressure, systemic vascular resistance, and blood gases. Also, the drug did not cause any cardiac arrhythmias or other side effects.

Conclusions

• Enoximone was found to have positive effects on heart rate and the volume of blood pumped in anaesthetized ponies. It did not cause significant changes in the blood pressure of the ponies. The observation that enoximone improved oxygen delivery despite an increase in venous admixture—the mixing of oxygenated and deoxygenated blood—suggests that it could have potential benefits in veterinary medicine.